The Longfield Gun Drilled 30-Spline Birfields are made out of 100% chromoly and are precision polished to remove any imperfections that may cause stress risers. The internals of the birfield are also made from 4340 chromoly and are dual heat treated for superior strength. The birfield has a M8 grease zerk at the end of the stub shaft and is gun drilled through the center of the birfield to allow for grease to pass through the zerk fitting and into the internals. This will save you precious time by eliminating the need to disassemble your axle just to service your birfields.
The Gun Drilled 30-Spline Birfields also have a shallow relief near the splines on the stub shaft known as a Machined Spline Saver. The Machined Spline Saver eliminates stress concentrations caused by grooving from the tool that makes the splines on the stub shaft. The stress concentration from the spline groove is a common failure point on birfield stub shafts.
The axle shafts are also made out of 4340 chromoly steel.
We understand that once you upgrade your axles, the next weak link is your hub gears, so we decided to include our Chromoly Inner and Outer Hub Gears and Creeper Drive Flanges at no additional cost!